The present invention relates to furniture. More particularly, this invention relates to chairs for positioning individuals in relaxing, comfortable, and/or healthful positions and to methods for making the same.
Chairs have existed for some time. More recently, relatively speaking, chairs that pivot and chair backs that fold have been developed. Another improvement consists of some form of leg support while a chair is in a reclined position. A particular type of reclining chair is a zero gravity chair.
The term zero gravity positioning relates to the orientation of the legs above the level of the heart. It is also called the “90-90” position and the Trendleberg position. The latter term is commonly used in hospitals when a bed is positioned with the legs elevated in order to reduce tension and improve blood circulation. The term “zero gravity,” or “Z.G.,” stems from suggestions that the human body naturally assumes a similar orientation with respect to the legs when relaxed and suspended in weightlessness. A zero gravity chair attempts to position its occupant in an orientation where the legs may be even with or above the human heart.
Most zero gravity chairs use a fixed relationship between a seat and a back which hold the user in a preset open angular position. An open position, where the angle between the legs and the torso is greater than 90 degrees, may be a beneficial part of zero gravity positioning when the user is reclined. The open angle helps to insure that discs in a user's back are not compressed which may cause back discomfort and possibly damage over time. However, the human body varies in shape from person to person, and thus, the optimum open angle for each person also may be different. Furthermore, a manufacturer's predefined open angle may not always be a comfortable open angle when the zero gravity chair backrest is in the upright position and the seat is level or near level. In the upright position, a smaller angle between the seat and backrest may be preferred. For example, the user may be reading or conversing with the backrest forward and a smaller angle than that of a typical zero gravity chair can provide greater back support and comfort. With a fixed relationship between the seat and the back, as is typical of a zero gravity chair, a difficulty arises in providing both an optimal zero gravity open angle as well as an optimal upright open angle.
Another issue with a fixed open angle positioning is that users of most zero gravity chairs may feel as though they are sliding forward when the chair is in the upright position. A larger fixed open angle of a typical zero gravity chair may cause many users to actually slouch because the predefined open angle may not hold the user comfortably in the seat. Further, because the body weight of the user may have slid forward, many users of a manual zero gravity chair with a fixed open angle may find the chair difficult to operate because the center of gravity of the user is not properly positioned in the chair.
It is therefore an object of the invention to provide a manual zero gravity chair with an adjustable backrest in relation to the seat section of the zero gravity chair. Another object of the invention is to provide the zero gravity chair with a user adjustable backrest independent of the various zero gravity positions the chair is capable of allowing.